IDoSeaDoo
Well-Known Member
I have a 97 Challenger w/ single 787. Rebuilt top end in Dec, running everything stock. Was running autolite 65's to break it in (these plugs are invincible to fouling!). It's what the guys at Advance crossed the NGKs to, but I'm not sure if these plugs were the right heat range. I simply forgot to swap them out for the correct NGKs. Anyway, the motor broke in perfectly, had 150psi on both holes. Was running it quite often the entire winter despite my pump cavitation. (I know, I know, shoulda fixed that). Anyway, I had four people on it last sunday and we managed to plane out, minutes before the crank gave up.
Upon disassembly, I found that the rear cyl had 90psi while front was at 140. Piston crowns looked good with normal wear. Cyl walls looked ok. With jugs removed I saw that the crank bearing failed and the c-rod actually moves up/down on the crack itself. Not sure how old that thing is, probably from '96. The plugs were pretty brown, like a coffee color. The PTO was a lighter color, but I also found signs of water intrusion on the dome. Closer inspection of the jugs showed burned out head gasket rings. Also, I noted that the lower expansion pipe was super heated and even changed color. The paint actually peeled off around the cone and the exhaust hose had a hole in it :facepalm: I didn't think it was running that lean, as the high needles were turned out 1/4 on each cyl, but now I suspect otherwise. Seems that it's not enough to compensate for the cold air (45-70 degF). So anyone have any theories as to why the crank gave out? What should I do to prevent this in the future? If the cylinders are w/in spec dimensionally, any reason I shouldn't re-use them w/ another bottom end?
Thanks guys
Upon disassembly, I found that the rear cyl had 90psi while front was at 140. Piston crowns looked good with normal wear. Cyl walls looked ok. With jugs removed I saw that the crank bearing failed and the c-rod actually moves up/down on the crack itself. Not sure how old that thing is, probably from '96. The plugs were pretty brown, like a coffee color. The PTO was a lighter color, but I also found signs of water intrusion on the dome. Closer inspection of the jugs showed burned out head gasket rings. Also, I noted that the lower expansion pipe was super heated and even changed color. The paint actually peeled off around the cone and the exhaust hose had a hole in it :facepalm: I didn't think it was running that lean, as the high needles were turned out 1/4 on each cyl, but now I suspect otherwise. Seems that it's not enough to compensate for the cold air (45-70 degF). So anyone have any theories as to why the crank gave out? What should I do to prevent this in the future? If the cylinders are w/in spec dimensionally, any reason I shouldn't re-use them w/ another bottom end?
Thanks guys
